Understanding TFCI, TPC, and Pilot Power Offsets

TFCI, TPC, and Pilot Power offsets (PO), which are applied to downlink control channels (DPCCH), are relative to the transmit power for data channels (DPDCH). Usually, these offsets are set to a positive value (see the figure below). The intent is to transmit control symbols at a higher level than data symbols, to maintain the link between mobile and base. Because only the DPCCH transmit power is offset, the total transmit power is minimized and less noise is generated in the system.

The figure below shows that the channel has the data transmit power (Power) set to 0.00 dB with the following offsets: TPC Power set to 3.00 dB, TFCI Power set to 2.00 dB, and Pilot Power set to 1.00 dB. Because of these offsets, the control symbols corresponding to TPC, TFCI, and Pilot will transmit at 3.00 dB, 2.00 dB, and 1.00 dB respectively.